Field of the Invention
The present invention relates to a vehicle seat, and more particularly, to a vehicle seat which is capable of mitigating whiplash of an occupant upon a collision accident by allowing the occupant's head to be closest to a headrest when the occupant sits down on the vehicle seat.
Description of Related Art
Generally, the seat provided to a vehicle needs to give comfort to an occupant when the occupant sits down thereon and in addition, sufficiently protect the occupant when an emergency situation such as a rear-end collision accident occurs.
Such a vehicle seat includes a seat cushion for supporting the lower body of an occupant, a seat back for supporting the upper body of an occupant, and a headrest coupled to a top end of the seatback to adjust the height thereof to support the head and neck region of an occupant.
Meanwhile, a neck injury of a seat occupant, which most often occurs upon a rear-end collision accident while a vehicle is stopping, is called a whiplash injury.
It has been known that the whiplash injury, that is, the injury of a neck region is caused due to a relative velocity difference between the head and torso of an occupant. When the vehicle is struck from the rear, the torso of the occupant moves forward due to an impact on the seatback but the head stays at rest, so that sharing force acts on the neck region. The sharing force has an abrupt impact upon the joints and muscles of the neck, resulting in the injury of a neck joint region.
To prevent the neck injuries, there has been developed an active headrest which is a headrest device for enhancing the safety of an occupant and allows the headrest to move to a position adjacent to the head of the occupant when a collision accident occurs. It is a trend to mitigate the neck injury of an occupant by using the active headrest.
Basically, the active headrest allows the headrest to move forward to support the head of an occupant when a collision accident occurs, such that the neck injury of the occupant is prevented. The active headrest is classified into an electronic system in which an actuator is operated according to an collision signal when a sensing unit senses a rear-end collision to transmit the collision signal to the actuator of the headrest, and a mechanical device in which the headrest moves forward by using the force of pushing the back or hips of the occupant against a seat when a rear-end collision accident occurs.
FIG. 1 is a schematic view illustrating a mechanical-type active headrest according to the related art. When a rear-end collision occurs, the back of an occupant pushes against a pressing plate 11 of a seatback while the occupant moves rearward, so that a support frame 13 of an upper side moves forward by a leverage principle while a link 12 located in the back of the pressing plate 11 is pushed rearward.
Thus, a headrest stay 14 inserted into the support frame 13 and a headrest body 15 move together forward to support the head of an occupant, so that a neck injury caused when the head is tilted back is prevented.
Mechanical-type active headrests are disclosed in Korean Patent No. 10-0551844 (Feb. 6, 2006) and Korean Unexamined Patent Publication No. 10-2005-0115108 (Dec. 7, 2005), and an electro-type active headrest is disclosed in Korean Unexamined Patent Publication No. 10-2014-0068660 (Jun. 9, 2005), as the documents of the related art.
As another technique for mitigating a neck injury of a vehicle seat, a sliding headrest used by adjusting front and rear positions of a headrest has been proposed. The sliding headrests are disclosed in Korean Patent No. 10-1033881 (May 2, 2011) and Korean Patent No. 10-1054755 (Aug. 1, 2011) as the documents of the related art.
Meanwhile, in a stage of developing a vehicle or a vehicle seat, a neck injury examination of measuring cervical vertebra and muscle injuries due to the movements of a head and a torso is conducted.
As shown FIG. 2, according to the neck injury test, after a dummy is fixed to a seat, the items related to an impact on a neck, the degree of neck bending and the degree of injury caused when the head of the dummy is tilted back and forth by causing a rear-end collision are evaluated.
In addition, as shown in FIG. 3, the considerations for reducing a neck injury in designing a seat includes static performance factors such as a backset and a height, where the backset represents a distance between a head and a headrest and the height represents a height difference between the head and the headrest.
The backset and height represent a shape and a position of a headrest which is the most important element for reducing a neck injury. The smaller the backset has a value, the more the neck injury is reduced. However, a small backset value causes interference between the head of an occupant and the headrest, so that the occupant may feel uncomfortable.
When taking the comfort of an occupant into account, there is a need to maintain a suitable backset value between the head of an occupant and the headrest. When taking the safety of an occupant into consideration, there is a need to allow the headrest to be placed at the nearest position to the head of an occupant.
Thus, when a seat is designed in consideration of the performance of reducing a neck injury, the comfort of an occupant may deteriorate.
As described above, the technique of reducing a neck injury such as an active headrest or a sliding headrest is mainly focused on the performance of reducing a neck injury, so that occupants complain about the degradation of comfort.
In particular, since the active headrest requires a plurality of additional components, the cost and weight are increased. In addition, an occupant may feel a foreign object at a top end of the seatback at which the pressing plate is placed, so that the comfort may deteriorate.
In addition, since a space exists between the head of an occupant and the headrest in all types of active headrests, the head is not limited until the headrest supports the head while moving forward when a rear-end collision occurs.
Therefore, when a long time is taken until the headrest supports the head of an occupant, a neck region of the occupant may be injured for the time.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.